Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 59, Num. 2, 2011, pp. 204-207

Neurology India, Vol. 59, No. 2, March-April, 2011, pp. 204-207

Original Article

Meningiomas: Correlation of Ki67 with histological grade

Sashidhar Babu¹, Shantveer G Uppin¹, Megha S Uppin¹, Manas Kumar Panigrahi², Vijay Saradhi³, Suchanda Bhattacharjee³, BP Sahu³, AK Purohit³, Sundaram Challa¹

¹ Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad, India
² Department of Neurosurgey, Krishna Institute of Medical Sciences, Hyderabad, India
³ Department of Neurosurgey, Nizam's Institute of Medical Sciences, Hyderabad, India

Correspondence Address: Sundaram Challa, Department of Pathology, Nizam's Institute Medical Sciences, Hyderabad - 500082, Andhra Pradesh, India, challa_sundaram@yahoo.com

Date of Submission: 30-Aug-2010
Date of Decision: 05-Oct-2010
Date of Acceptance: 26-Dec-2010

Code Number: ni11059

PMID: 21483118

DOI: 10.4103/0028-3886.79140

Abstract

Keywords: Invasion, Ki67 labeling index, meningioma, recurrent, WHO 2007 criteria

Introduction

Meningiomas are common primary central nervous system (CNS) tumors and account for about 30% of primary adult intracranial tumors. ^[1] They are usually slow-growing tumors with a female predominance. Meningiomas are classified into three grades according to World Health Organization (WHO) 2007. ^[2] The grading has implications on management. Grade I tumors are treated with surgery alone whereas Grade II and III are treated with surgery and radiotherapy. ^[3],[4] Despite complete total resection, 7-20% of benign (Grade I), 29-40% of atypical (Grade II), 50-78% of anaplastic (Grade III) meningiomas recur. ^[5] Grading system based on histopathological features has certain limitations in predicting the exact biological behavior of meningioma. The other factors implicated in tumor recurrence are extent of surgery, age, gender, location and brain invasion. ^[6],[7] Hence the use of ancillary techniques is necessitated to predict the tumor growth and recurrence. The net growth rate of a tumor is a balance between cell proliferation and apoptosis. Amongst the various techniques available to measure cell proliferation, Ki67 is the most widely used immunohistochemical marker. Ki-67 is a non-histone protein that is expressed in the proliferative phase of the cell cycle. It is a simple technique that can be applied on formalin-fixed paraffin-embedded sections.

In this paper, we studied Ki67 labeling index (LI) in the various histological subtypes and grades of meningioma and correlated it with the various parameters known for recurrence. To the best of our knowledge, this is the largest series from India including 300 meningiomas classified according to the WHO 2007 criteria and studied with Ki67 LI.

Material and Methods

This was a retrospective study of patients with intracranial and intraspinal meningiomas diagnosed at the Department of Pathology during the period 2005-08. The study was approved by the institutional ethics committee. The medical records of the patients were reviewed and details of age, gender, clinical presentation, location and recurrence if any were noted. The histological sections were reviewed and all tumors were graded according to WHO criteria 2007. ^[2] Immunohisochemistry with epithelial membrane antigen (EMA) and vimentin was done in histological subtypes of chordoid, clear cell, papillary and rhabdoid meningioma using monoclonal antibodies (DAKO USA). Presence or absence of brain invasion was noted in all tumors. Meningiomas with brain invasion were classified as atypical (Grade II) meningiomas. Immunohistochemistry with Ki67 was performed in as many samples as possible.

Ki-67 immunohistochemistry technique

Sections of 5-micron thickness collected on poly-L-lysine coated slides were subjected to immunohistochemistry by indirect immunoperoxidase technique. Briefly, the sections were dewaxed in two changes each in xylene and alcohol and stabilized in 0.1 M phosphate buffer saline (PBS) solution. Antigen retrieval was performed by high-temperature unmasking using pressure cooker (125 ^o C for 30 sec at 25 lbs pressure). Sections were then cooled at room temperature and immersed in 3% methanol hydrogen peroxide for blocking endogenous peroxidase activity. Following blockage of non-specific binding sites using 3% casein, sections were incubated in primary antibody (Ki67, monoclonal antibody, 1:50, DAKO, USA) for 1 h, followed by incubation in secondary antibody for 30 min (Polymer detection kit, Biogenix, USA). Antigen-antibody complex was visualized by using diaminobenzidine as chromogen. Sections were counterstained with Harris Hematoxylin, dehydrated and mounted in DPX. At least 1000 nuclei were counted at high magnification (40Χ objective) without recounting same areas and the average was expressed as percentage. Foci of necrosis were excluded [Figure - 1].

Statistical analysis

The statistical analysis done in this study was ANOVA (Analysis of variance between groups) and unpaired t test. The test is significant when P value is <0.05. The details of the test type used are mentioned in [Table - 1] and [Table - 2].

Results

There were 429 meningiomas diagnosed during the study period and immunohistochemistry with Ki67 was done in 300 samples. Further analysis was restricted to meningiomas where Ki67 LI was available. There were 115 males and 185 females. The age ranged from 2 to 75 years with mean age of 45.8 years. There were 11 children below the age of 18 years. Convexity was the commonest location. There were 211 Grade I, 78 Grade II and 11 Grade III meningiomas. Transitional meningioma was the commonest subtype of meningioma. Grade II meningiomas included four each of clear cell and chordoid and 70 atypical meningiomas. Grade III meningiomas included two papillary, one rhabdoid and eight anaplastic meningiomas. [Table - 1] gives Ki67 LI in 300 meningiomas with respect to age, gender, location and histological subtype. There was female predominance and the mean age was in the fifth decade in all grades. In children, 8/11 (72.73%) meningiomas were atypical (Grade II). The mean grade-wise Ki67 LI for males versus females was not statistically significant [Table - 2]. [Table - 2] also gives significance of Ki67 LI in all meningiomas with respect to gender, location and recurrent tumors. The mean Ki67 LI increased from Grade I to II and from Grade II to III and this difference statistically significant. The Ki67 LI for histological subtypes chordoid, clear cell, papillary and rhabdoid was high but there was no statistical significance between the subtypes. There were 290 intracranial and 10 spinal meningiomas. Ki67 LI between intracranial and spinal meningiomas was not statistically significant and this could be attributed to the disproportion of numbers in the two groups. Convexity was the commonest location and transitional meningioma was the commonest subtype [Table - 1]. Meningiomas at convexity, basal region, falx and parasagittal locations showed statistical significance with Ki67 LI grade-wise; however, at other locations; there was no statistical significance. There were 55 meningiomas showing brain invasion. These included 49 Grade II and six Grade III tumors. The mean Ki67 LI grade-wise for brain-invasive versus non-invasive tumors was statistically significant [Table - 2]. There were 23 recurrent meningiomas. The mean Ki67 LI between recurrent and non-recurrent meningiomas was statistically significant [Table - 2]. The Ki67 LI for meningiomas at initial surgery was not available.

Discussion

Meningiomas most commonly occur in middle-aged and elderly patients with a female predominance. Meningiomas that occur in males and in children tend to behave aggressively and recur. There were conflicting reports in the literature about the influence of age and gender on the proliferative potential of meningiomas and recurrence. Ilidian et al, reported that age and gender has no influence on proliferative activity. ^[8] Kasuya et al, reported that male gender was an independent risk factor for high proliferative potential. ^[9] The mean Ki67 LI with respect to age and gender was not statistically significant in our series. Eight out of 11 tumors in children were Grade II tumors. Location was one of the factors implicated in recurrence. Meningiomas of the skull base and tumors close to major sinuses were reported to have a high proliferative index and were associated with recurrence. ^[8],[9] Tumors at convexity, basal region, falx, and parasagittal region showed statistical significance grade-wise with Ki67 LI. All spinal tumors in our series were Grade I and had Ki 67 LI in the range of 2.5000 ± 3.61 and none of them were recurrent.

Grade-I meningiomas constituted about 90%, Grade-II about 7% and Grade-III about 2% of the meningiomas in various reported series. ^{[5],[6],[10],[11],[12]} Our results were similar to the earlier reported series. Histopathologic grading is one of the important predictors of recurrence. Ki67 LI correlates with histological grade and recurrence. However, all the tumors in each grade do not behave uniformly. ^[9] Kasuya et al, reported that 56 out of 296 Grade-I tumors, 27 out of 28 Grade-II tumors and 17 out of 18 Grade-III tumors had MIB-1 staining index ≥ 3. ^[9] Ilidian et al, reported that atypical meningiomas were heterogeneous and had two groups i.e. tumors with low proliferative grade and tumors with high proliferative grade. ^[8] Increased MIB-1 labeling indices were associated with an increased risk of recurrence and emphasized that they can be used as an accessory to grading meningiomas. ^[13] The Ki67 LI increased with the grade of meningiomas and mean Ki67 LI between Grade I and II and I and III were statistically significant in our series. This is in agreement with other reported series. ^[4],[14] There was no statistically significant difference in the Ki67 LI between the histological subtypes in each grade in our series.

Brain invasion is defined as irregular tongue-like protrusions of tumor into brain parenchyma without leptomeninges. ^[11] Brain-invasive meningiomas are prognostically equivalent to Grade-II meningiomas and not all of them are histologically atypical. They tend to recur and behave like atypical meningiomas. ^[2] So all brain-invasive meningiomas were classified as atypical meningiomas according to the WHO 2007 classification of CNS tumors. The Ki67 LI was high in brain-invasive meningiomas when compared to noninvasive meningiomas and it was statistically significant [Table - 2].

In our study there were 23 recurrent meningiomas. The Ki67 LI was not available at the time of initial surgery. The Ki 67 LI of recurrent tumors when correlated with that of non-recurrent tumors was statistically significant. In our study the majority of the recurrent tumors were Grade II. The mean Ki67 LI in recurrent tumors was 10.018±8.94 and in non-recurrent ones was 6.4580±6.29. Guarnaschelli et al, suggested that meningothelial meningiomas were the most common in benign recurrent meningiomas. ^[15] Perry et al, in a study of 62 cases of meningiomas suggested that Ki67 LI in excess of 4.2% was indicative of high tumor proliferation activity and recurrence. ^[5] Ho et al, suggested a cutoff value of 10 for Ki67 LI as the most accurate predictor of recurrence. ^[16] As Ki67 LI varies among individual laboratories, long-term follow-up studies are required to establish these values. Maes et al, studied recurrent and non-recurrent meningiomas with Ki67 and human telomerase catalytic submit (hTERT) and opined that Ki67 was a good marker of proliferation potential but not a good predictor of recurrence as no statistically significant differences were found between recurrent and non-recurrent meningiomas. ^[17] We have not correlated the extent of surgical resection and Ki67 LI as the number of recurrent tumors was small in our series. Extent of surgery is a very important and independent prognostic marker for recurrence. Currently, molecular characterization and gene profiling studies are underway to define the biological behavior of meningiomas. ^[13],[18] To conclude, high Ki67 LI indicates higher grade of meningioma and possible recurrence.

References

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